Study: Inhaled Nanotubes Could Pose Cancer Risk

May 27, 2008

Some forms of carbon nanotubes could be as harmful as asbestos if inhaled in sufficient quantities, according to a study published in Nature Nanotechnology.

Researchers said the study used established methods to see if specific types of nanotubes have the potential to cause mesothelioma -- a cancer of the lung lining. Light as plastic and stronger that steel, carbon nanotubes are being developed for use in new drugs, energy-efficient batteries and futuristic electronics. But since their discovery, questions have been raised about whether some of these nanoscale materials may cause harm and undermine a nascent market for all types of carbon nanotubes, including multi- and single-walled carbon nanotubes.

Anthony Seaton, MD, a co-author on the paper and a professor emeritus at the University of Aberdeen in the United Kingdom, said, "While there are reasons to suppose that nanotubes can be used safely, this will depend on appropriate steps being taken to prevent them from being inhaled in the places they are manufactured, used and ultimately disposed of. Such steps should be based on research into exposure and risk prevention, leading to regulation of their use. Following this study, the results of which were foreseen by the Royal Society in the U.K. in 2004, we can no longer delay investing in such research."

Researchers, led by Professor Kenneth Donaldson at the University of Edinburgh in the United Kingdom, examined the potential for long and short carbon nanotubes, long and short asbestos fibers, and carbon black to cause pathological responses known to be precursors of mesothelioma. Material was injected into the abdominal cavity of mice -- a sensitive predictor of long fiber response in the lung lining.

Donaldson stressed there are still pieces of the puzzle to fill in. "We still don't know whether carbon nanotubes will become airborne and be inhaled, or whether, if they do reach the lungs, they can work their way to the sensitive outer lining. But if they do get there in sufficient quantity, there is a chance that some people will develop cancer -- perhaps decades after breathing the stuff."

However, short or curly carbon nanotubes did not behave like asbestos, "and by knowing the possible dangers of long, thin carbon nanotubes, we can work to control them," Donaldson said.

Donaldson added that the present study only tested for fiber-like behavior and did not exonerate carbon nanotubes from damaging the lungs in other ways. "More research is still needed if we are to understand how to use these materials as safely as possible," he stated.